Risk factors of secondary cancer in laryngeal, oropharyngeal, or hypopharyngeal cancer after definitive therapy.

BACKGROUND: Our previous research showed that a high rate of secondary carcinogenesis is observed during follow-up after transoral surgery in patients with early-stage laryngeal, oropharyngeal, and hypopharyngeal cancers. We speculate that the contributing factors are alcohol drinking, smoking, and aging; however, we could not provide clear evidence. In this study, we aimed to identify the risk factors for secondary carcinogenesis in patients with these cancers, particularly factors associated with drinking and/or smoking. METHODS: The medical records of all-stage laryngeal, oropharyngeal, and hypopharyngeal cancer patients who had undergone definitive treatment were retrospectively analyzed. Assessments included visual and endoscopic observations of the primary site, enhanced cervical CT or US of the primary site and regional lymph nodes, PET-CT, and enhanced whole-body CT. Clinical characteristics were compared in patients with and without secondary carcinogenesis and in patients with hypopharyngeal cancer and patients with other cancers. RESULTS: Hypopharyngeal cancer was an independent risk factor for secondary cancer. The 5-year incidence rate of secondary cancer was 25.5%, 28.6%, and 41.2% in laryngeal, oropharyngeal, and hypopharyngeal cancers, respectively. Radiotherapy was defined as an independent risk factor in hypopharyngeal cancer patients with secondary cancers. No direct correlation was found between secondary carcinogenesis and alcohol consumption, smoking, or aging. CONCLUSIONS: Patients with hypopharyngeal cancer require close follow-up as they are at high risk of developing secondary cancer, possibly because out-of-field radiation exposure may induce systemic secondary carcinogenesis in hypopharyngeal cancer patients with genetic abnormality induced by alcohol consumption.

Detailed clinical features and genotype-phenotype correlation in an OTOF-related hearing loss cohort in Japan.

Mutations in the OTOF gene are a common cause of hereditary hearing loss and the main cause of auditory neuropathy spectrum disorder (ANSD). Although it is reported that most of the patients with OTOF mutations have stable, congenital or prelingual onset severe-to-profound hearing loss, some patients show atypical clinical phenotypes, and the genotype-phenotype correlation in patients with OTOF mutations is not yet fully understood. In this study, we aimed to reveal detailed clinical characteristics of OTOF-related hearing loss patients and the genotype-phenotype correlation. Detailed clinical information was available for 64 patients in our database who were diagnosed with OTOF-related hearing loss. As reported previously, most of the patients (90.6%) showed a "typical" phenotype; prelingual and severe-to-profound hearing loss. Forty-seven patients (73.4%) underwent cochlear implantation surgery and showed successful outcomes; approximately 85-90% of the patients showed a hearing level of 20-39 dB with cochlear implant and a Categories of Auditory Performance (CAP) scale level 6 or better. Although truncating mutations and p.Arg1939Gln were clearly related to severe phenotype, almost half of the patients with one or more non-truncating mutations showed mild-to-moderate hearing loss. Notably, patients with p.His513Arg, p.Ile1573Thr and p.Glu1910Lys showed "true" auditory neuropathy-like clinical characteristics. In this study, we have clarified genotype-phenotype correlation and efficacy of cochlear implantation for OTOF-related hearing loss patients in the biggest cohort studied to date. We believe that the clinical characteristics and genotype-phenotype correlation found in this study will support preoperative counseling and appropriate intervention for OTOF-related hearing loss patients.

A risk factor for newly diagnosed secondary cancer in patients with early-stage laryngeal, oropharyngeal, or hypopharyngeal cancer: sub-analysis of a prospective observation study.

BACKGROUND: We previously identified hypopharyngeal cancer as an independent risk factor for the incidence of newly diagnosed secondary cancers after the treatment of early-stage laryngeal, oropharyngeal, and hypopharyngeal cancers. We subsequently used a different patient cohort to validate the usefulness of this factor during the follow-up period in these patients. METHODS: Patients who underwent transoral surgery (TOS) as a definitive treatment between April 1, 2016, and September 30, 2020, were included. The incidence of secondary cancer was evaluated in hypopharyngeal and other cancers. Overall survival (OS), recurrence-free survival (RFS), and disease-free survival (DFS) outcomes were evaluated. Statistical analyses based on the risk factors were also performed. RESULTS: Incidence of new secondary cancer was 30% in hypopharyngeal cancer patients as compared to 11% in other cancer patients, and the risk was 3.60-fold (95% confidence interval 1.07-12.10) higher after definitive treatment for initial head and neck cancers. The 3-year OS, RFS, and DFS rates were 98%, 86%, and 67%, respectively. CONCLUSIONS: Among patients with early-stage laryngeal, oropharyngeal, and hypopharyngeal squamous cell carcinoma, who were initially treated with TOS, hypopharyngeal cancer patients had a higher risk of newly diagnosed secondary cancers as observed during the follow-up period.

Establishment of PDX-derived salivary adenoid cystic carcinoma cell lines using organoid culture method.

To generate a reliable preclinical model system exhibiting the molecular features of salivary adenoid cystic carcinoma (ACC) whose biology is still unclear due to the paucity of stable cell cultures. To develop new in vitro and in vivo models of ACC, the techniques of organoid culture and patient-derived tumor xenograft (PDX), which have attracted attention in other malignancies in recent years, were applied. Tumor specimens from surgically resected salivary ACC were proceeded for the preparation of PDX and organoid culture. The orthotopic transplantation of patient-derived or PDX-derived organoids was demonstrated into submandibular glands of NSG mice and those histology was evaluated. PDX-derived organoid cells were evaluated for the presence of MYB-mediated fusion genes and proceeded for in vitro drug sensitivity assay. Human ACC-derived organoids were successfully generated in three-dimensional culture and confirmed the ability of these cells to form tumors by orthotopic injection. Short-term organoid cell cultures from two individual ACC PDX tumors were also established that maintain the characteristic MYBL1 translocation and histological features of the original parent and PDX tumors. Finally, the establishment of drug sensitivity tests on these short-term cultured cells was confirmed using three different agents. This is the first to report an approach for the generation of human ACC-derived organoids as in vitro and in vivo cancer models, providing insights into understanding of the ACC biology and creating personalized therapy design for patients with ACC.

The incidence of newly diagnosed secondary cancer; sub-analysis the prospective study of the second-look procedure for transoral surgery in patients with T1 and T2 head and neck cancer.

BACKGROUND: Our prospective study of patients with early T-stage head and neck cancer indicated a high incidence of newly diagnosed secondary malignancies during the follow-up period. We aimed to determine the incidence rate and risk factors of secondary malignancies in early-stage head and neck cancer patients. METHODS: We sub-analyzed the patient data of a previous study focusing on secondary cancer incidence. The endpoints were statistical analyses of risk factors and survival and incidence rates. RESULTS: The incidence rate of secondary cancer was 37%, the crude incidence of second primary cancers was 10.6 per 100 person-years, and the 5 year secondary cancer-free survival rate was 63%. The hypopharynx as the primary site was an independent significant predictive factor (odds ratio 3.96, 95% confidence interval 1.07-14.6, p = 0.039). CONCLUSIONS: Early stages of laryngeal, oropharyngeal, and hypopharyngeal cancer had a risk of secondary cancer, especially hypopharyngeal cancer. Attention to the secondary cancer has to be paid during the follow-up period after controlling the early-stage disease. These findings highlight the need for awareness of the incidence of secondary cancer in cases of early-stage primary head and neck cancer.

Validation of the risk factors for primary control of early T-stage laryngeal, oropharyngeal, and hypopharyngeal squamous cell carcinoma by transoral surgery: a prospective observational study.

BACKGROUND: We had previously identified the following risk factors for insufficient control of early T-stage head and neck cancer by transoral surgery (TOS): (1) tumor thickness > 7 mm on enhanced computed tomography (CT), and (2) poor differentiation in pathological examination. We subsequently used a different patient cohort to validate the usefulness of these factors in determining the need for adaptation of TOS. STUDY SETTING: A prospective observational study METHODS: Patients who received TOS as a definitive treatment between April 1, 2016 and September 30, 2020 were included. Primary control rates (by single TOS and TOS alone) in relation to the above-mentioned risk factors were calculated. Overall (O), recurrence-free (RF), and disease-free (DF) survival (S) outcomes were evaluated. A combination analysis based on the number of risk factors was also performed. RESULTS: Patients with tumor thickness > 7 mm had a 2.88-fold [95% confidence interval (CI) 1.01-8.51] higher risk of incomplete primary resection by single TOS, while patients who showed poor differentiation on pathological assessments had a 13.14-fold (95% CI 3.66-47.14) higher risk of insufficient primary control by TOS alone. The 3 year OS, RFS, and DFS rates were 99%, 83%, and 63%, respectively. Patients with both risk factors had a 93.00-fold (95% CI 4.99-1732.00) higher risk of incomplete primary control by TOS alone. CONCLUSIONS: Among patients with early-stage laryngeal, oropharyngeal, and hypopharyngeal squamous cell carcinoma, primary control by TOS alone may not be achieved in patients with both risk factors, that is, tumor thickness > 7 mm as measured by enhanced CT and poor differentiation on pathological examination.

An effective screening strategy for deafness in combination with a next-generation sequencing platform: a consecutive analysis.

The diagnosis of the genetic etiology of deafness contributes to the clinical management of patients. We performed the following four genetic tests in three stages for 52 consecutive deafness subjects in one facility. We used the Invader assay for 46 mutations in 13 genes and Sanger sequencing for the GJB2 gene or SLC26A4 gene in the first-stage test, the TaqMan genotyping assay in the second-stage test and targeted exon sequencing using massively parallel DNA sequencing in the third-stage test. Overall, we identified the genetic cause in 40% (21/52) of patients. The diagnostic rates of autosomal dominant, autosomal recessive and sporadic cases were 50%, 60% and 34%, respectively. When the sporadic cases with congenital and severe hearing loss were selected, the diagnostic rate rose to 48%. The combination approach using these genetic tests appears to be useful as a diagnostic tool for deafness patients. We recommended that genetic testing for the screening of common mutations in deafness genes using the Invader assay or TaqMan genotyping assay be performed as the initial evaluation. For the remaining undiagnosed cases, targeted exon sequencing using massively parallel DNA sequencing is clinically and economically beneficial.

Predictive markers, including total lesion glycolysis, for the response of lymph node(s) metastasis from head and neck squamous cell carcinoma treated by chemoradiotherapy.

BACKGROUND: Chemoradiotherapy (CRT) is used to treat cervical lymph node(s) metastatic head and neck cancer patients. Evaluation and treatment of lymph node(s) after CRT is important to improve the prognosis. METHODS: Prior to CRT, we determined the TNM stage by visual and imaging examinations. Metabolic tumor volume (MTV) and total lesion glycolysis (TLG) were calculated from the results of fluorodeoxyglucose-positron emission tomography (FDG-PET). After CRT, the patients were divided in two groups-complete response (CR) and non-CR-and their responses were compared with the clinical characteristics. RESULTS: T4, N2b, N2c and TLG2.5 ≥ 18.8 were statistically significant predictive indices before CRT. The odds ratio, 95 % confidence interval and p value were, respectively-T4: 2.73, 1.15-6.51, 0.0230; N2b: 6.96, 1.50-32.3, 0.0132; N2c: 11.80, 2.37-58.50, 0.00258; and TLG2.5 ≥ 18.8: 6.25, 2.17-18.00, 0.000672. CONCLUSIONS: TLG was found to be a good predictive factor for metastatic lymph node(s) prior to CRT treatment. After CRT treatment, FDG-PET was found to be highly specific and useful for negative screening.

Treatment results and prognostic factors for advanced squamous cell carcinoma of the head and neck treated with salvage surgery after concurrent chemoradiotherapy.

BACKGROUND: For primary organ preservation, concurrent chemoradiotherapy (CCRT) is performed for advanced squamous cell carcinoma of the head and neck (SCCHN). In this organ-preservation setting with CCRT, surgery is reserved as a salvage treatment in cases of locoregional failure after CCRT. The purpose of the study was to review our experience with salvage surgery after CCRT for patients with SCCHN and to evaluate the effectiveness and prognostic factors affecting survival. METHODS: The records of patients with stage II-IVB SCC of the larynx, oropharynx, or hypopharynx treated with salvage surgery after CCRT between 1998 and 2012 were reviewed. RESULTS: A total of 645 patients with previously untreated, resectable SCC of the larynx, oropharynx, or hypopharynx received CCRT. Salvage surgery was performed for 78 of 225 patients with residual or recurrent tumors. The 5-year overall survival (OS) and disease-specific survival rates for patients who received salvage surgery were 61.0 and 65.5 %, respectively. Stage IV, poorly differentiated, synchronous double cancer, and surgical complications were significant predictors of unfavorable OS on multivariate analysis. Postoperative complications were observed in 30 patients (38.5 %). CONCLUSIONS: Salvage surgery is the best therapeutic option for failure after CCRT for SCCHN because of its good survival rate, although a high surgical complication rate is seen. Patients with initial stage IV tumors, poorly differentiated SCC, or synchronous double cancer are considered for further adjuvant treatment.

Imaging strategy for response evaluation to chemoradiotherapy of the nodal disease in patients with head and neck squamous cell carcinoma.

BACKGROUND: Definitive chemoradiotherapy (CRT) is used to treat lymph node metastatic head and neck cancer patients. Regional control of the neck disease is important to improve the prognosis, and the accuracy of the method used to evaluate the metastatic lymph node(s) after CRT is crucial to the decision-making process for any following salvage surgery. METHODS: Patients undergoing CRT were divided in two groups of patients of those showing complete clinical response (CR) and those showing clinical non-response (non-CR), as assessed by computed tomography (CT) and/or magnetic resonance imaging (MRI), ultrasonography, fluorodeoxyglucose-positron emission tomography (FDG-PET), and fine needle aspiration cytology. The responses (CR vs. non-CR) were compared with the actual clinical outcomes. For the interim analysis, the study period was broken down into two periods, namely, the exploratory phase (patients treated between January 2002 and April 2012) and the validating phase (patients treated between May 2012 and January 2014). RESULTS: The sensitivity, specificity, and accuracy were as follows: CT and/or MRI, 66.7, 73.8, and 72.8 %, respectively, in the exploratory phase; ultrasonography, 91.7, 70.6, and 73.4 %, respectively, in the exploratory phase and 80.0, 82.8, and 82.4 %, respectively, in the validating phase; FDG-PET, 50.0, 97.5, and 91.3 %, respectively, in the exploratory phase and 60.0, 100, and 94.1 %, respectively, in the validating phase; cytology, 68.4, 95.9, and 90.3 %, respectively, in the exploratory phase and 66.7, 100, and 85.7 %, respectively, in the validating phase. CONCLUSIONS: Based on our results, CT and/or MRI appear to be inadequate methods for the evaluation of the response of lymph node(s) to CRT. In contrast, ultrasonography appears to be a highly sensitive and useful tool for positive screening at 6-8 weeks after CRT, and FDG-PET appears to be a highly specific and useful tool for negative screening at 8-12 weeks after CRT.

Two Cases of Masticator Space Abscess Spreading from Infections of the Mandibular Teeth.

The masticator space is located between the masseteric fascia and the pterygoid muscle fascia. Here we report two cases of masticator space abscesses spreading from infections of mandibular teeth. Case 1 is an 85-year-old lady who were referred to Yokohama City University Hospital with a left-cheek swelling and trismus. An enhanced CT scan revealed an abscess extending from the left infratemporal fossa to the temporal fossa. A purulent discharge was observed from her left lower gingiva. We performed surgical drainage under general anesthesia. After infection control, the affected teeth were extracted. Case 2 is an 82-year-old lady who was administered oral bisphosphonate for osteoporosis. She presented to another hospital with fever, trismus and swelling anterior to the right ear after right lower tooth extraction. Because MRI revealed persistent osteomyelitis of her mandible even after antibiotic treatment, she was referred to us. Enhanced CT showed an abscess in the right infratemporal fossa. After surgical drainage similar to Case 1, antibiotics were administered for approximately 4 months to control the osteomyelitis.　 It is important to recognize that infections of the mandibular teeth can cause an abscess in the masticator space through the pterygomandibular and infratemporal spaces.

Novel PTPRQ mutations identified in three congenital hearing loss patients with various types of hearing loss.

OBJECTIVES: We present 3 patients with congenital sensorineural hearing loss (SNHL) caused by novel PTPRQ mutations, including clinical manifestations and phenotypic features. METHODS: Two hundred twenty (220) Japanese subjects with SNHL from unrelated and nonconsanguineous families were enrolled in the study. Targeted genomic enrichment with massively parallel DNA sequencing of all known nonsyndromic hearing loss genes was performed to identify the genetic cause of hearing loss. RESULTS: Four novel causative PTPRQ mutations were identified in 3 cases. Case 1 had progressive profound SNHL with a homozygous nonsense mutation. Case 2 had nonprogressive profound SNHL with a compound heterozygous mutation (nonsense and missense mutation). Case 3 had nonprogressive moderate SNHL with a compound heterozygous mutation (missense and splice site mutation). Caloric test and vestibular evoked myogenic potential (VEMP) test showed vestibular dysfunction in Case 1. CONCLUSION: Hearing loss levels and progression among the present cases were varied, and there seem to be no obvious correlations between genotypes and the phenotypic features of their hearing loss. The PTPRQ mutations appeared to be responsible for vestibular dysfunction.

Concurrent chemoradiotherapy with docetaxel, cisplatin and 5-fluorouracil (TPF) in patients with locally advanced squamous cell carcinoma of the head and neck.

OBJECTIVE: Compared with radiotherapy alone, concurrent chemoradiotherapy significantly improves survival rates for patients with squamous cell carcinoma of the head and neck. The aim of this study was to retrospectively evaluate the efficacy, toxicity and long-term prognosis of concurrent chemoradiotherapy with docetaxel, cisplatin and 5-fluorouracil chemotherapy. METHODS: A total of 140 patients were enrolled and evaluated. Patients were received two cycles of docetaxel, cisplatin and 5-fluorouracil chemotherapy (docetaxel [50 mg/m(2): Day 1], cisplatin [60 mg/m(2): Day 4] and continuous 5-fluorouracil [600 mg/m(2)/day: Days 1-5]) during definitive radiotherapy. RESULTS: The overall response rate was 97.1%. The 3 and 5-year overall survival rates were 83.3 and 79.2%, respectively. The 3 and 5-year disease-specific survival rates were 84.2 and 80.0%, respectively. Among patients with laryngeal or hypopharyngeal carcinoma, the 5-year laryngectomy-free survival rate was 64.9%. CONCLUSIONS: Concurrent chemoradiotherapy with docetaxel, cisplatin and 5-fluorouracil showed excellent survival and organ preservation rates for the patients with locally advanced squamous cell carcinoma of the head and neck.

[The accuracy of evaluating the response of metastatic lymph nodes after concurrent chemoradiotherapy in patients with head and neck squamous cell carcinoma].

BACKGROUND: Concurrent chemoradiotherapy (CCRT) is used to treat advanced head and neck cancer. The accuracy of evaluating lymph nodes metastases following CCRT is important for subsequent therapy. PATIENTS AND METHODS: Patients were divided into two groups according to the nodal status, the complete response (CR) and the non-CR groups, as determined by imaging and fine-needle aspiration cytology (FNAC) performed 4-8 weeks after the CCRT, and the findings were compared with the status 6 months after the treatment completion. RESULTS: The sensitivity, the specificity, positive predictive value, negative predictive value and accuracy of each evaluation method were as follows: 66.7%, 73.5%, 26.7%, 93.8% and 72.5%, respectively, for computer tomography (CT) and magnetic resonance imaging (MRI); 91.7%, 69.9%, 30.6%, 98.3% and 72.6% for ultrasonography (US) ; 50.0%, 96.4%, 66.7%, 93.0% and 90.5% for fluorodeoxyglucose-positron emission tomography (FDG-PET) or PET-CT; and 68.4%, 96.1%, 81.3%, 92.5% and 90.6% for FNAC. CONCLUSION: To evaluate the response of lymph node(s) treated by CCRT, US is useful as a positive screening tool and FDG-PET and PET-CT as negative screening tools. FNAC is useful in evaluating suspicious lymph nodes in both positive and negative cases.

Detailed Clinical Features of PTPRQ-Associated Hearing Loss Identified in a Large Japanese Hearing Loss Cohort.

The PTPRQ gene has been identified as one of the genes responsible for non-syndromic sensorineural hearing loss (SNHL), and assigned as DFNA73 and DFNB84. To date, about 30 causative PTPRQ variants have been reported to cause SNHL. However, the detailed clinical features of PTPRQ-associated hearing loss (HL) remain unclear. In this study, 15,684 patients with SNHL were enrolled and genetic analysis was performed using massively parallel DNA sequencing (MPS) for 63 target deafness genes. We identified 17 possibly disease-causing PTPRQ variants in 13 Japanese patients, with 15 of the 17 variants regarded as novel. The majority of variants identified in this study were loss of function. Patients with PTPRQ-associated HL mostly showed congenital or childhood onset. Their hearing levels at high frequency deteriorated earlier than that at low frequency. The severity of HL progressed from moderate to severe or profound HL. Five patients with profound or severe HL received cochlear implantation, and the postoperative sound field threshold levels and discrimination scores were favorable. These findings will contribute to a greater understanding of the clinical features of PTPRQ-associated HL and may be relevant in clinical practice.

[A case report: a repeated cerebrospinal fluid otorrhea].

Cerebrospinal fluid (CSF) otorrhea, leakage of CSF through the ear structures, may occur from a traumatic or operative defect in the skull, tumor, cholesteatoma, or congenital anomalies. A case of repeated CSF otorrhea is uncommon. In this report, we presented a case of a repeated CSF otorrhea which occurred a decade after the first middle ear surgery for chronic otitis media. The first CSF leakage, which might have been due to bone defects in the tegmen at the first middle ear sutgery, was surgically repaired using a transmastoid approach. However, CSF leakage with a meningoencephalocele occurred again 8 years after our first surgery for the CSF and the fistula was repaired using a transmiddle cranial fossa approach. Although 2 years have passed since the surgery, the CSF leakage has not recurred.

Biphenotypic Sinonasal Sarcoma: A Genetically Confirmed Case Showing Bone Invasion Accompanying a Non-neoplastic Respiratory Epithelium.

Biphenotypic sinonasal sarcoma is a newly established tumor entity that is associated with distinct clinicopathological findings. Biphenotypic sinonasal sarcoma is a rare, low-grade spindle cell sarcoma that arises in middle-aged females, exclusively in the sinonasal tract. A fusion gene involving PAX3 is detected in most biphenotypic sinonasal sarcomas, which aids in its diagnosis. Here, we report a case of biphenotypic sinonasal sarcoma with its cytological findings. The patient was a 73-year-old woman who presented with purulent nasal discharge and dull pain in the left cheek area. Computed tomography showed a mass extending from the left nasal cavity to the left ethmoid sinus, the left frontal sinus, and the frontal skull base. She underwent a combined transcranial and endoscopic approach for en bloc resection with a safety margin. Histologically, spindle-shaped tumor cells have been thought to proliferate mainly in the subepithelial stroma. Here, nasal mucosal epithelial hyperplasia was noted, and the tumor had invaded the bone tissue accompanying the epithelial cells. Fluorescence in situ hybridization (FISH) analysis showed a PAX3 rearrangement, and next-generation sequencing identified a PAX3::MAML3 fusion. Based on FISH, split signals were observed not in respiratory cells but in stromal cells. This indicated that respiratory cells were non-neoplastic. In the diagnosis of biphenotypic sinonasal sarcoma, the inverted growth of the respiratory epithelium can be a diagnostic pitfall. FISH analysis using a PAX3 break-apart probe is helpful not only for an accurate diagnosis but also for detecting the true neoplastic cells.

P4HA1 Promotes Cell Migration and Colonization in Hypopharyngeal Squamous Cell Carcinoma.

BACKGROUND/AIM: This study aimed to identify key molecules associated with the survival of patients with hypopharyngeal squamous cell carcinoma (HpSCC) by combining in silico and in vitro analyses. MATERIALS AND METHODS: Differentially expressed genes (DEGs) were screened using the Gene Expression Omnibus database. For DEGs, we performed functional enrichment and protein-protein interaction network analyses to identify potential biological functions and hub genes. Functional analysis of HpSCC cell lines verified the critical roles of the hub genes. RESULTS: DEGs were associated with the extracellular matrix. Among the hub genes, high expression of prolyl 4-hydroxylase subunit alpha 1 (P4HA1) was significantly associated with shorter survival. In addition, P4HA1 knockdown inhibited cell migration and colonization. Suppression of cell proliferation was demonstrated using P4HA1-selective inhibitors. CONCLUSION: P4HA1 may be a useful therapeutic target for the treatment of HpSCC.

Reduced PLP1 expression in induced pluripotent stem cells derived from a Pelizaeus-Merzbacher disease patient with a partial PLP1 duplication.

Pelizaeus-Merzbacher disease (PMD) is an X-linked recessive disorder characterized by dysmyelination of the central nervous system (CNS). We identified a rare partial duplication of the proteolipid protein 1 gene (PLP1) in a patient with PMD. To assess the underlying effect of this duplication, we examined PLP1 expression in induced pluripotent stem (iPS) cells generated from the patient's fibroblasts. Disease-specific iPS cells were generated from skin fibroblasts obtained from the indicated PMD patient and two other PMD patients having a 637-kb chromosomal duplication including entire PLP1 and a novel missense mutation (W212C) of PLP1, by transfections of OCT3/4, C-MYC, KLF4 and SOX2 using retro-virus vectors. PLP1 expressions in the generated iPS cells were examined by northern blot analysis. Although PLP1 expression was confirmed in iPS cells generated from two patients with the entire PLP1 duplication and the missense mutation of PLP1, iPS cells generated from the patient with the partial PLP1 duplication manifesting a milder form of PMD showed null expression. This indicated that the underlying effect of the partial PLP1 duplication identified in this study was different from other PLP1 alterations including a typical duplication and a missense mutation.